CVE-2026-40864

mediumpriority · track · 27EPSS 0.002 · 7 %ileexploit · PoCEUFRUS

grimoire priorityP1 · Urgent

Exploitable?

Public exploit

1 exploit · PoC

Likely / severe?

0.18% (7th) EPSS

CVSS 4.3 · medium

Is it mine?

4 products

Check your exposure

Who says so?

5 sources

cnnvd · enisa_euvd · osv · nvd

EPSS · scored 2026-10-24

JupyterHub is software that allows users to create a multi-user server for Jupyter notebooks. In versions 4.1.0 through 5.4.4, XSRF protection (updated in 4.1.0) inappropriately treated requests with Sec-Fetch-Mode: no-cors as same-origin requests, bypassing XSRF checks. The JSON API is not affected, only HTTP form endpoints, such as /hub/spawn and /hub/accept-share, meaning attackers could trigger server spawn (but not access the server) and if the attacker is a JupyterHub user permitted to share access to their server, cause a user to accept a share and have access to the attacker's server. This issue has been fixed in version 5.4.5. If developers are unable to immediately upgrade, they can temporarily mitigate this issue by dropping requests to JupyterHub with Sec-Fetch-Mode: no-cors if they are using a reverse proxy.

cvss

Technical severity, 0–10. One row per scoring source.

5.4

010

base score 0–10 · higher = more severe · hover a vector to decode

v3.14.3mediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:Nprimary · NVD / NIST USexploitability 2.8 · impact 1.4

v3.15.4mediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:Lsecondary · ENISA EU

v3.15.4mediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:Lsecondary · security-advisories@github.comexploitability 2.8 · impact 2.5

v3.15.4mediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:Lsecondary · OSV

v3.14.1mediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N/E:Psecondary · CVSS-BT (t0sche)

ssvc

A stakeholder decision — act, attend, or track — from exploitation and impact.

Trackcoordinatorcisa_ssvcUS

weaknesses

The CWE weakness classes this flaw belongs to.

CWE-352USCWE-352US

exploits (1)

Public proof-of-concept and weaponised exploit code.

romain-deperne/CVE-2026-40864JupyterHub CSRF via cross-origin form POST — CVE-2026-40864 / CVSS 5.4PoC · poc_in_github

affected products (4)

Products and version ranges known to be affected.

jupyterhub jupyterhub4.1.0, → 5.4.5enisa_euvdEU
jupyter jupyterhub4.1.0 → 5.4.5nvdUScpe:2.3:a:jupyter:jupyterhub:*:*:*:*:*:*:*:*
Bitnami jupyterhub4.1.0 → 5.4.5osvUSpkg:bitnami/jupyterhub
PyPI jupyterhub4.1.0 → 5.4.5osvUSpkg:pypi/jupyterhub

advisories (4)

Vendor and ecosystem advisories describing this.

GHSA-m68r-v472-jgq9JupyterHub has cross-origin form POSTs bypass XSRF (CWE-352)2026-05-05ghsa · osvUS
## Summary JupyterHub's XSRF protection (updated in 4.1.0) inappropriately treated requests with `Sec-Fetch-Mode: no-cors` as same-origin requests, which they are not, bypassing XSRF checks. The JSON API is not affected, only HTTP form endpoints, such as `/hub/spawn` and `/hub/accept-share`, meaning attackers could trigger server spawn (but not access the server) and if the attacker is a JupyterHub user permitted to share access to their server, cause a user to accept a share and have access to the attacker's server. ## Patches Upgrade to JupyterHub 5.4.5. ## Mitigations If a reverse proxy is in use, drop requests to JupyterHub with `Sec-Fetch-Mode: no-cors`.
BIT-jupyterhub-2026-40864JupyterHub: Cross-origin form POSTs bypass XSRF2026-05-28vendor · osvUS
JupyterHub is software that allows users to create a multi-user server for Jupyter notebooks. In versions 4.1.0 through 5.4.4, XSRF protection (updated in 4.1.0) inappropriately treated requests with Sec-Fetch-Mode: no-cors as same-origin requests, bypassing XSRF checks. The JSON API is not affected, only HTTP form endpoints, such as /hub/spawn and /hub/accept-share, meaning attackers could trigger server spawn (but not access the server) and if the attacker is a JupyterHub user permitted to share access to their server, cause a user to accept a share and have access to the attacker's server. This issue has been fixed in version 5.4.5. If developers are unable to immediately upgrade, they can temporarily mitigate this issue by dropping requests to JupyterHub with Sec-Fetch-Mode: no-cors if they are using a reverse proxy.
CERTFR-2026-AVI-1378Multiples vulnérabilités dans les produits IBMFrançais2026-10-23vendor · certfrFR
PYSEC-2026-21892026-05-22vendor · osvUS
JupyterHub is software that allows users to create a multi-user server for Jupyter notebooks. In versions 4.1.0 through 5.4.4, XSRF protection (updated in 4.1.0) inappropriately treated requests with Sec-Fetch-Mode: no-cors as same-origin requests, bypassing XSRF checks. The JSON API is not affected, only HTTP form endpoints, such as /hub/spawn and /hub/accept-share, meaning attackers could trigger server spawn (but not access the server) and if the attacker is a JupyterHub user permitted to share access to their server, cause a user to accept a share and have access to the attacker's server. This issue has been fixed in version 5.4.5. If developers are unable to immediately upgrade, they can temporarily mitigate this issue by dropping requests to JupyterHub with Sec-Fetch-Mode: no-cors if they are using a reverse proxy.

also known as (7)

Other names and identifiers for this entity.

sources

Which sources assert this record, and when.

cnnvd enisa_euvd osv nvd certfr NVD CVE.org MITRE

published 2026-05-22modified 2026-07-23

references (7)

External citations — patches, advisories, analysis.

scry

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